The present invention relates to orthotic devices that aid in the rehabilitation and restoration of muscular function in patients with impaired muscular function or control. More particularly, the present invention relates to orthotic devices and configurations of these orthotic devices suitable for therapeutic use with patients that have impaired neuromuscular/muscular function of the appendages, including, but not limited to, orthotic devices including of a motorized system of braces and related control systems that potentiate improved function of the appendages for activities such as walking.
Millions of individuals suffer from either partial or total loss of walking ability, resulting in greatly impaired mobility for the afflicted individual. This disabled state can result from traumatic injury, stroke, or other medical conditions that cause disorders that affect muscular control. Regardless of origin, the onset and continuance of walking impairment can result in additional negative physical and/or psychological outcomes for the stricken individual. In order to improve the health and quality of life of patients with walking impairment, the development of devices and methods that can improve or restore walking function is of significant utility to the medical and therapeutic communities. Beyond walking impairment, there are a range of medical conditions that interfere with muscular control of the appendages, resulting in loss of function and other adverse conditions for the affected individual. The development of devices and methods to improve or restore these additional functions is also of great interest to the medical and therapeutic communities.
Human exoskeleton devices are being developed in the medical field to restore and rehabilitate proper muscle function for people with disorders that affect muscle control. These exoskeleton devices can be represented as a system of motorized braces that can apply forces to the wearer's appendages. In a rehabilitation setting, exoskeletons are controlled by a physical therapist and/or the patient wearing the exoskeleton who uses one of a plurality of possible inputs to command an exoskeleton control system. In turn, the exoskeleton control system actuates the position of the motorized braces, resulting in the application of force to, and typically movement of, the body of the exoskeleton wearer.
Exoskeleton control systems prescribe and control trajectories in the joints of an exoskeleton. These trajectories can be prescribed as position based, force based, or a combination of both methodologies, such as those seen in an impedance controller. Position based control systems can modify exoskeleton trajectories directly through modification of the prescribed positions. Force based control systems can modify exoskeleton trajectories through modification of the prescribed force profiles. Complicated exoskeleton movements, such as walking, are commanded by an exoskeleton control system through the use of a series of exoskeleton trajectories, with increasingly complicated exoskeleton movements requiring an increasingly complicated series of exoskeleton trajectories. These series of trajectories may be cyclic, such as the exoskeleton taking a series of steps with each leg, or they may be discrete, such as an exoskeleton rising from a seated position into a standing position.
Depending on the particular physiology or rehabilitation stage of a patient, different degrees of assistance must be provided by the exoskeleton in various motions required for walking. For some patients, such as paraplegics, the actuators of a modern exoskeleton must provide all of the force required for walking. However, in some applications where a patient has some function, it may be sufficient to simply provide a push in the correct direction at the correct position in the gait cycle. This sort of locomotion assistance can be likened to pushing a child on a swing: the push provided need not be precise as long as it is neither so small that motion of the swing decays nor so large that the motion of the swing becomes unstable. Thus, it is possible for an exoskeleton to facilitate the walking of a patient by simply providing some assistance at a key portion of the gait cycle.
In people who have limited use of their lower limbs, restoring the function of the knee is critical to the restoration of standing or walking function because the leg cannot bear weight without a functioning knee. This is made clear within the field of prosthetics where the greatest effort and complexity of design is dedicated to the design of knee prostheses. Historically, knee prostheses were the first to incorporate microprocessors and later powered actuators as well. In the field of orthotics, conventional mechanical devices include braces that lock when the knee is straight and unlock in later stance so that the person can bend their knee during swing; these devices have been available for decades, although recent advances have rendered them smaller and more reliable. Newer orthotics, like prosthetics, have come to include microprocessors which allow for greater robustness to variable conditions. For example, in a traditional, purely mechanical orthosis, locking the knee for stance is triggered by reaching full knee extension in terminal swing. However, it may be desirable for the knee to lock in terminal swing even if the knee extension is not full, by using other markers such as looking for impact with the support surface using an accelerometer. Such behaviors are extremely difficult to design mechanically, but can be trivial to implement with a microprocessor. There are many examples of such devices known to the art, some of which are available for sale.
Existing knee orthosis devices have many shortcomings. Firstly, a stance control knee brace cannot provide active assistance to help a person go from sitting to standing. Some devices have the ability to power a person's gait. That is, in addition to having a microprocessor that can lock the knee at a fixed position, the device also has an actuator large enough to transfer mechanical power into the person's gait. The additional complexity required is non-trivial: the only actuation systems practical are electric motors using large (typically around 1:100) transmission ratios that convert the high speed, low torque motion of the motor into high torque, low speed motion needed for human locomotion. In some devices, this transmission is a ball screw device; in others a harmonic drive; and in others a hydraulic pump and cylinder. In all cases, there is a common difficulty besides the actuation, in that the device must be coupled to the person. Superficially, this may not appear to be a limiting factor since so many unpowered stance control knee braces have been designed, but in fact there is an important difference. Stance controlled knee braces are designed only to support body weight when the knee is nearly straight; in this situation, the torque resisted by the device is small. Powered knee braces can provide torque even when the knee angle is large, and are designed to produce very large torques often similar to those produced by the human body. In these cases, attempting to couple to the person is not a trivial problem, as the large torque generated by the device at the knee must be resolved through the person-device connection at both the thigh and the shank. This connection is typically soft, so as not to injure the person, and, as a result, applying high torque results in undesirable person-device motion. With this in mind, there exists an unmet need to provide a device by which a powered knee brace can exert sufficiently large forces on the knee of the person coupled to the knee brace so as to affect walking by the person coupled to the knee brace, while simultaneously decreasing relative motion between the person and the knee brace device. This device must also do so without producing undue discomfort or awkwardness to the patient coupled to the device.
An orthotic device with a powered knee brace alone can neither assist in the swinging of the leg, nor in the propulsion of the body during stance. Biomechanically, the hip plays a role in both functions, helping propel the person during stance and throw the leg forward during swing. While devices have been proposed to aid with the hip motion of the person during walking, these devices are cumbersome because they require high power actuation and/or close anthropomorphic coupling to the person. The human hip is a three degree of freedom joint, allowing motion in all three rotational axes; and while high powers for walking are required only in the sagittal plane, unpowered degrees of freedom must often be provided in the other axes in order to allow for normal walking. Some devices approximate these degrees of freedom with complex mechanisms, and others simply lock out these degrees of freedom, constraining the person. Therefore, an unmet need also exists to provide an orthotic hip device that allows assistance of leg movement in swing and propulsion of the body in stance, but without restricting degrees of freedom about the hip or requiring overly complicated, bulky, heavy mechanisms.
For some persons suffering from lower extremity weakness (often, but not always, post stroke), preventing foot drop is important, because otherwise the person may drag their toe on the ground, stumble, and fall. Therefore, an unmet need further exists to provide a device that is able to reliably lift the toe for the person during swing.